fflush(3C) Standard C Library Functions fflush(3C)
fflush - flush a stream
#include <stdio.h>
int fflush(FILE *stream);
If stream points to an output stream or an update stream in which the
most recent operation was not input, fflush() causes any unwritten data
for that stream to be written to the file, and the st_ctime and
st_mtime fields of the underlying file are marked for update.
If stream is a null pointer, fflush() performs this flushing action on
all streams for which the behavior is defined above. Additionally, an
input stream or an update stream into which the most recent operation
was input is also flushed if it is seekable and is not already at end-
of-file. Flushing an input stream discards any buffered input and
adjusts the file pointer such that the next input operation accesses
the byte after the last one read. A stream is seekable if the underly‐
ing file is not a pipe, FIFO, socket, or TTY device. An input stream,
seekable or non-seekable, can be flushed by explicitly calling fflush()
with a non-null argument specifying that stream.
Upon successful completion, fflush() returns 0. Otherwise, it returns
EOF and sets errno to indicate the error.
The fflush() function will fail if:
EAGAIN
The O_NONBLOCK flag is set for the file descriptor underlying
stream and the process would be delayed in the write operation.
EBADF The file descriptor underlying stream is not valid.
EFBIG An attempt was made to write a file that exceeds the maximum file
size or the process’s file size limit; or the file is a regular
file and an attempt was made to write at or beyond the offset
maximum associated with the corresponding stream.
EINTR The fflush() function was interrupted by a signal.
EIO The process is a member of a background process group attempting
to write to its controlling terminal, TOSTOP is set, the process
is neither ignoring nor blocking SIGTTOU, and the process group
of the process is orphaned.
ENOSPC
There was no free space remaining on the device containing the
file.
EPIPE An attempt is made to write to a pipe or FIFO that is not open
for reading by any process. A SIGPIPE signal will also be sent to
the process.
The fflush() function may fail if:
ENXIO A request was made of a non-existent device, or the request was
beyond the limits of the device.
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
getrlimit(2), ulimit(2), attributes(5)
SunOS 5.9 27 Mar 2001 fflush(3C)